Substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonanilides such as those described in EP Application 142152A published May 22, 1985 are valuable herbicides for the selective control of weeds in agronomic crops. A known method for the preparation of substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonanilides involves the reaction of substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonyl halides with either a substituted aniline in the presence of a tertiary amine base (EP Application 142152A) or an excess of aniline (British Pat. No. 951,652). This type of procedure is generally satisfactory for the preparation of substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonanilides wherein the substituted aniline employed is aniline itself or is a substituted derivative of aniline that has similar reactivity as a nucleophilic reagent. When the substituted aniline reactant is of substantially reduced nucleophilic reactivity due to the presence of electron withdrawing substituents on the ring and, especially, to the presence of such substituents in the positions ortho to the amino function, this method is very slow and provides low yields of the desired products. This reactivity problem is particularly unfortunate because the most herbicidally potent substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonanilides possess such substituents.
In order to circumvent the reactivity problem, Kleschick et al. (EP Application 142152A) employed a strong base, such as an alkali metal alkyl or an alkali metal hydride, capable of converting the poorly nucleophilic substituted aniline to its corresponding metal derivative in place of the tertiary amine base. The metal derivative was preformed and then allowed to react with a substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonyl halide. This procedure allows the compounds to be prepared, but it requires an excess of the metal derivative of the substituted aniline and is carried out below 0.degree. C., and, therefore, is not commercially desirable. In view of the herbicidal properties of substituted 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonanilides, it is desirable to have improved processes for their preparation that produce them in high yields and in a relatively short reaction period.